xfs: set prealloc flag in xfs_alloc_file_space()

Now that we only call xfs_update_prealloc_flags() from
xfs_file_fallocate() in the case where we need to set the
preallocation flag, do this in xfs_alloc_file_space() where we
already have the inode joined into a transaction and get
rid of the call to xfs_update_prealloc_flags() from the fallocate
code.

This also means that we now correctly avoid setting the
XFS_DIFLAG_PREALLOC flag when xfs_is_always_cow_inode() is true, as
these inodes will never have preallocated extents.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Author: dgchinner

fs/xfs/xfs_bmap_util.c

@@ -850,9 +850,6 @@ xfs_alloc_file_space(
 			rblocks = 0;
 		}
 
-		/*
-		 * Allocate and setup the transaction.
-		 */
 		error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
 				dblocks, rblocks, false, &tp);
 		if (error)
@@ -869,9 +866,9 @@ xfs_alloc_file_space(
 		if (error)
 			goto error;
 
-		/*
-		 * Complete the transaction
-		 */
+		ip->i_diflags |= XFS_DIFLAG_PREALLOC;
+		xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+
 		error = xfs_trans_commit(tp);
 		xfs_iunlock(ip, XFS_ILOCK_EXCL);
 		if (error)

fs/xfs/xfs_file.c

@@ -908,7 +908,6 @@ xfs_file_fallocate(
 	struct inode		*inode = file_inode(file);
 	struct xfs_inode	*ip = XFS_I(inode);
 	long			error;
-	enum xfs_prealloc_flags	flags = 0;
 	uint			iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 	loff_t			new_size = 0;
 	bool			do_file_insert = false;
@@ -1006,8 +1005,6 @@ xfs_file_fallocate(
 		}
 		do_file_insert = true;
 	} else {
-		flags |= XFS_PREALLOC_SET;
-
 		if (!(mode & FALLOC_FL_KEEP_SIZE) &&
 		    offset + len > i_size_read(inode)) {
 			new_size = offset + len;
@@ -1057,11 +1054,6 @@ xfs_file_fallocate(
 			if (error)
 				goto out_unlock;
 		}
-
-		error = xfs_update_prealloc_flags(ip, XFS_PREALLOC_SET);
-		if (error)
-			goto out_unlock;
-
 	}
 
 	/* Change file size if needed */